The investigators have shown in three pilot studies that intra-articular metallic gold microparticles can reduce knee osteoarthritis pain for up to two years. These results are noteworthy considering the growing number of older adults who suffer from osteoarthritis pain, which contributes to increased demand on healthcare resources. Demonstrating effective treatment could alleviate this burden for a significant portion of the aging population.

The specific aim is to evaluate whether intra-articular metallic gold microparticles are superior to placebo in reducing the need for additional treatment in patients with knee osteoarthritis within one year. The investigators will test the hypothesis that intra-articular metallic gold microparticles reduce subsequent treatment events by more than 50% compared to placebo during this period.

To test the superiority of metallic gold microparticles over a placebo, 240 patients will be included in a randomized, double-blind, controlled trial. This process will take place over a period of 1-2 years. The study will follow the CONSORT Guidelines and comply with the Danish Data Protection Agency. The investigators will handle all data in an electronic form, including demographics and all outcome measures. The investigators will use an electronic Case Report Form (CRF). The management of data will be handled according to the Danish Data Protection Agency's guidelines. The host for data will be physically located at Aalborg University Research Data host, and at North Denmark Region, q-drive host, and follow the Guidelines from The Danish Protection Agency. The schedule for randomization will be randomly generated using a computer before the initiation of the trial. The medical doctor will be blind to group allocation and will not be involved in providing the metallic gold microparticles or placebo. The participants and the medical doctor performing follow-up will be blind to group allocation.

All patients will receive either intra-articular metallic gold microparticles and HA or HA alone. With the use of 2 cc syringe, the investigators will perform intra-articular injection using the standard approach for knee puncture and injection. For intervention, 20 mg metallic gold microparticles (72.000 particles, 20-40 µm) will be injected into the joint using 2 mL hyaluronic acid. For control, 2 mL of hyaluronic acid will be injected into the joint. A centralized computer-generated randomization will allocate to either 2 cc of hyaluronic acid with or without 20 mg metallic gold microparticles.

At the end of the trial, the patients in the control group will receive the intervention treatment with metallic gold microparticles.

Inclusion Criteria:

• more than 6 months of knee pain without efficacy on pain of conservative treatment, radiographic knee osteoarthritis according to Kellgren-Lawrence grade 1-4, and age ≥18years

Exclusion Criteria:

• malalignment, indication for knee replacement surgery, malignancy, active infection and antibiotic treatment, active treatment with steroids, biological or other anti-Rheumatic medication, inability to comply with the protocol, inadequacy in the written and spoken national language

After the publication of the study:

February 2029